very slow in connecting to filezilla server

[knarfoe]

Hello,

I have the following setup:

A: Windows Server 2016
B: Windows 10 workstation
C: Windows 10 workstation

Initializing a connection from B to C goes quickly and fine.
From A to C it is very slow. Like 20-25 seconds. All other activity is slow also, like changing from one remote folder to another. (Retrieving Directory listing)
Turning firewalls off does not help.

What things should I check first to make things better?

thanks

[botg]

How are the machines connected to each other? Try a single cable plugged on one end directly into the server and on the other end directly into the client.

[knarfoe]

There is just a switch in between.

[botg]

Are there many failed login attempts listed in the server log?